Rogue River-Siskiyou: Where the Klamath Mountains Meet the Cascades

The Rogue River-Siskiyou National Forest is two forests that were merged administratively, and the merger makes geographic sense. The Rogue River National Forest occupied the western flanks of the Cascades in southwestern Oregon. The Siskiyou National Forest covered the Klamath Mountains between the Cascades and the coast. Together, the merged forest covers about one point eight million acres of the most botanically diverse corner of Oregon.

The Klamath Mountains, of which the Siskiyou Mountains are a subrange, are an ancient oceanic plate scraped off the ocean floor by tectonic collision and welded onto the western edge of North America over hundreds of millions of years. The result is a geological jumble of rock types that produced an extraordinary range of soil chemistry, which in turn produced a botanical diversity that is disproportionate to the region's area. The Klamath-Siskiyou region is considered one of the world's twenty-five biodiversity hotspots, a designation usually reserved for tropical forests.

Port Orford cedar, native only to a stretch of the Oregon-California coast and the adjacent mountains, grows in the Siskiyou portion of the forest. The tree is threatened by Phytophthora lateralis, a water mold that has been moving through Port Orford cedar populations since the nineteen fifties, and for which there is no cure. The forest has instituted boot-cleaning stations and road restrictions to slow the spread.

The Illinois River, a tributary of the Rogue, runs through the Siskiyou with such clear water and intact riparian habitat that it was designated Wild and Scenic in nineteen eighty-four. The river is narrow and technical and almost entirely road-free in its lower canyon.